This invention is concerned with an extended reach drilling technique for providing a highly deviated wellbore that extends from a surface location, land or marine, essentially vertically into the earth and thereafter extends in a highly deviated attitude into the earth such that the wellbore penetrates a mineral-bearing formation at a subsurface location spaced a great lateral distance from the surface location.
Wellbores and wells have been drilled to extend into the earth in directions other than vertical for various reasons and by various techniques. A need for such wells was early recognized and still exists today for tapping mineral reserves located beneath water bodies or located beneath other poorly accessible surface locations. For example, before the turn of the century the Summerland Field located underwater near Santa Barbara, Calif. was drilled by whipstocking holes out under the water from land locations.
More recent developments have enabled ultrahigh-angle wellbores to be drilled and completed. Techniques for drilling ultrahigh-angle wellbores are sometimes referred to as "extended reach drilling", a term that has been coined to describe rotary drilling procedures used to drill wellbores greater than 60 degrees from the vertical and wherein complex wellbore profiles may be used to extend the horizontal limits of wellbores. Such techniques may be used to provide a wellbore that extends from a surface location to a subsurface location spaced a great lateral distance therefrom.
In an article entitled "Ultrahigh-Angle Wells Are Technical and Economic Success", THE OIL AND GAS JOURNAL, July 19, 1976, pp. 115-120, there is described a project wherein a well was drilled and completed to a 12,300-foot measured depth at an average angle of 82.degree.. In a paper, SPE 6818, "Improved Techniques For Logging High-Angle Wells" by M. W. Bratovitch, W. T. Bell, and K. D. Kaaz, which was presented at the 52nd Annual Fall Technical Conference and Exhibition of the Society of Petroleum Engineers of AIME in Denver, Colo., Oct. 9-12, 1977, it is said that high-angle wells are becoming commonplace, particularly in offshore areas. The paper describes work which contributes to increasing the deviation angles at which wells can be conventionally logged and to deciding whether to try gravity descent or pump-down tools as a first attempt at logging high-angle wells.
In U.S. Pat. No. 4,063,592 to Arthur H. Youmans, there is described a system for logging highly deviated earth boreholes which system is comprised of a conventional logging instrument that is adapted to transverse a slanted or deviated earth borehole on the end of a conventional logging cable.
In U.S. Pat. No. 3,285,350 to J. K. Henderson, there is described a technique for drilling off-vertical holes through earth formations and more particularly a technique and apparatus for controllably drilling holes through and substantially parallel to mineral formations between separated wells.